There are many devices for administering powdered medicaments to the lungs, which employ propellants, such as compressed gases, e.g. air, or liquefied gas propellants, to dispense and disperse the medicament.
There are also a number of known breath actuated inhalation devices for administering powdered medicaments to the lungs, which have mouthpieces through which the medicament is inhaled. British Patent Specification Nos. 1 521 000, 1 520 062, 1 472 650 and 1 502 150 disclose devices where a capsule is inserted into the device, which mitigates spillage of medicament prior to inhalation. Access to the medicament is gained by piercing the capsule or cutting it in half inside the dispensing device. On inhalation the air flows into or through the capsule and the powder within is released into the air stream and flows towards the mouth.
U.S. Pat. No. 4,210,140 discloses a device in which access to the powdered medicament is gained by pulling the halves of the capsule apart so that the medicament is emptied to a suitable position for entrainment in the airflow caused by inhalation.
U.S. Pat. No. 6,655,381 relates to a pre-metered dose assembly for consistently supplying precise doses of medicament for a breath-actuated dry powder inhaler. The assembly includes a cap defining a dry powder delivery passageway for providing air to a dry powder supply port of a swirl chamber of a breath-actuated dry powder inhaler, and a magazine including a plurality of reservoirs for holding pre-metered doses of dry powder. One of the magazine and the cap is movable with respect to the other of the magazine and the cap for sequentially positioning the reservoirs within the delivery passageway of the cap. A breath-induced low pressure at an outlet port of the inhaler causes an airflow through the dry powder delivery passageway of the assembly and into the dry powder supply port that entrains dry powder from the reservoir positioned in the passageway for inhalation by a patient using the inhaler. The passageway is provided with a venturi in the passageway by the reservoir to create a flow through the reservoir and bring the powder there from.
U.S. Pat. No. 4,446,862 to Baum et al. describes an inhaler device in which access to the powdered medicament is gained by pulling the halves of a capsule apart, leaving the lower half of the capsule retained in an upright position in the device, with its open end flush with the lower surface of a disc shaped inhalation chamber. Spaced around half the circumference of the chamber are a number of air inlets and, opposite these, a larger air outlet leading to a mouthpiece. On inhalation, air is drawn through the chamber and across the open mouth of the capsule. It is stated that this may create a resonance effect in the capsule, similar to the effect which causes a sound to be produced by blowing across the opening of a bottle.
US published patent application number 2009114220 to Boehringer discloses a powder inhaler device in which a powder cavity is provided with an air outlet opening into the lower surface of an air flow path which narrows in the region of the outlet opening. The cavity also has an air inlet which does not open into the flow path. A venturi is created by the narrowing flow path adjacent the outlet, giving rise to low pressure in this area when flow is generated by a user inhaling. Air is thereby drawn through the cavity from the inlet to the outlet and then into the flow path.
In spite of the numerous prior art devices there is a need for a device which is simple in design and therefore inexpensive, compact in size and also simple to operate, but which also allows for efficient emptying of a cavity of powder. Consistent and efficient emptying is important to avoid wastage of expensive medicament by leaving it in the device and to avoid residual powder contaminating the device and being inadvertently inhaled on subsequent uses of the device.
There is also a need for a device which efficiently deaggregates powder before being administered. It is desirable for the deaggregation process to result in a significant proportion of the powder particles being in a certain aerodynamic size range. This is often referred to as classifying the powder particles. Various ways of enabling deaggregation are described in the prior art. For example, tortuous flow paths can cause deaggregation as particles impact the walls of the flow path. Alternatively, obstructions can be placed in the flow path downstream of the powder cavity or reservoir. Vibrating or shaking is another possibility. U.S. Pat. No. 4,446,862, discussed above, provides for the capsule to be moved rapidly on inhalation to loosen the powder contents and thereby aid deaggregation of highly cohesive or compacted powders.
Devices employing deaggregation features in the downstream flow passage may become clogged or contaminated in use, since medicament powder may accumulate on these downstream features. It is of course desirable to reduce or avoid the risk of administering an inaccurate amount of medicament powder. Where powder accumulates on downstream deaggregation features, a risk is that accumulated powder from several doses may dislodge suddenly from these downstream features (e.g. if the device is dropped) resulting in the patient receiving a significant over-dose. Accordingly, there is a need to mitigate or eliminate downstream powder accumulation.